Re: Stream the schools not the children
There is another reason why selective schools suck.
Counter example: The one part of the UK where grammar schools survived and comprehensives didn't appear was N. Ireland. That was because the parents dug their heels in and the Labour government forcing that policy in the 1970's was too afraid of creating more instability at a bad time. That government fell before it could overcome the opposition.
Since then NI children from both grammar and non-grammar (secondary) schools have done systematically better (around 5-7%) in O/A level exams and their successors than the UK average.
There's some sign that this difference is flattening out. It roughly corresponds to when Tony Blair started his new crusade against grammar schools, despite paying to send his own children to a private one.
I went to a grammar school. The local secondary taught childen up to age 16, and those that wanted to continue to A-levels could then transfer to our grammar, which helped resolve the "late bloomer" issues.